blends work fine---some people always use blends- and mixing them is fine too- i would pre-wash though=the blends may not shrink as much as a 100% cotton- causing uneven seams/puckering.
blends are often a little heavier than the regular quilting cottons we use- so they make a heavier quilt- but they hold up well- generally do not bleed- pressing can be a bit different- (assuming they are a poly-cotton blend) you will want to use a cooler iron- so you don't scorch/melt the fabric.